Rainwebs

"What will happen if the RAINforests dry up?"

Climate change and food WEBS along a latitudinal gradient is a 4-years research project funded by the Programme Blanc 2012 of the French Agence Nationale de la Recherche. This project is coordinated by Régis Céréghino, Université Toulouse III - Paul Sabatier, France.RAINWEBS is part of a longer-term collaboration within the Bromeliad Working Group coordinated by Diane Srivastava, Univ. British Columbia, Vancouver, Canada.The general aims of RAINWEBS are: (1) to understand the interaction between biogeographic changes and climate change, and (2) to disseminate a robust, multi-regional theory of how climate affects ecosystems.

It has proven challenging to study the impacts of climate change on ecosystem processes, first because effects on single species cannot be extrapolated to the complex network of species interactions, second because it is difficult to manipulate entire ecosystems, and third because it is not clear how results from one location can be used to predict responses across entire regions when species show biogeographic turnover in composition and traits.

We manipulate a small, spatially discrete food web (the microbial-faunal food web inhabiting water-filled bromeliads) to determine the role of species interactions in determining ecosystem responses, and we take advantage of the fact that our focal food web occurs over a broad biogeographic gradient to examine the generality of food web responses. We concentrate on precipitation because it is understudied (compared to temperature) and has potentially profound impact for ecosystems, and on Neotropical ecosystems which are expected to lose more species than their temperate counterparts.

We experimentally change precipitation entering bromeliad ecosystems from baseline levels, to study effects on the bromeliad food web and ecosystem functions in 3 field sites covering the range of faunal diversity in the Americas: French Guiana, the centre of bromeliad radiation and a hotspot for bromeliad faunal diversity, Costa Rica which has a moderate species pool, and Puerto Rico, a Caribbean site with a depauperate species pool. If we understand the mechanisms underlying biogeographic effects, we can consider how our results can be extrapolated to unstudied portions of the biogeographic gradient.

Our major findings will be disseminated to scientists, students, stakeholders, and public schools. Ecologists have a limited timeframe in which studies on consequences of climate change will be useful to society, so need to seek shortcuts by which results from particular field sites can be extrapolated to other regions with differing species pool. This project provides a fresh approach on how to predict the ecosystem consequences of climate change.